Process and apparatus for manufacturing ammonium nitrate



Dec. 14, 1937. J. H. sHApLElGH ZZS PROCESS AND APPARATUS FOR MANUFACTURING AMMONIUM NITRATE Filed Jan. 18, 1935 2 Sheets-Sheet l Dec. M, 1937., J. H. sHAPLEiGH PROCESSl AND APPARATUS FOR MANUFACTURING AMMONIUM NITRATE Filed Jan. 18, 1935 2 Sheets-Sheet 2 MI M Patented Dec. 14, 1937 Y* omiso srArs PATENT OFFICE PRooEss AND Y APPARATUS Foa MANU- V1'Ao'rURI1\Ta AMMONIUM NITRATE James H. Shapleigh, Wilmington,

Del., assignor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Application-January 1s, 1935, serial No. 2,350 zo claims. (oies-'103) A This invention relates tothe manufacture of inorganic nitrates and more specifically, to a 1 method and apparatus for the absorption of a mixture ofV nitrogen oxide and oxygen in an D trative purposes will be described in detail with reference to the production of Vammonium nitrate. Y Y

in conventional manufacture of ammonium nitrate heretofore, nitric acid, produced by,rfor example, the ammoniaY oxidation Yprocess and of a concentration of about.3545% HNO3, was placed in an acidproof tub, and below the surface thereof a stream of aqua ammonia, or Vof gaseous ammonia was run in. Asineutralization 7 proceeded, more and more nitric acid was run into the tub in order to keep the contents on the acid side and to prevent loss of ammonia as gas. VAt the end of the operation, the contents of the tub were brought to'neutrality, removed to an evaporator,

the solution by steam ,coil's,'and the molten ammonium nitrate was run out into crystallizing pans or kettles.

It will be noted that in this operation it was first necessary7 to produce aqueous nitric acid,

tion, again expend energy, as heat, to remove the Ysuperfluous water.

Now in accordance with this invention an improved method and apparatus for producing 'ammonium nitrate are provided, which overcome many of the difficulties of prior processes and apparatus in an eiiicient and economical manner.

,m One of the objects of this invention is to produce crystallized ammonium nitrateV from amrrnonia and air or oxygen, with evaporation only of the water produced in the oxidation of said ammonia.

Yt Essentially, the improved process accordingtoV .55 reaction from the` solution, the solution is re- Y' where the water was removedV fromV cool it, thus wasting heat, and, after neutralizai turnedto the top of Ythe Vabsorption tower, where it againV goes through the samecycle.

y "As the quantity ofammonium nitrate `solution circulating through the system increases in bulk, a proportion of it is periodically drawn off and, after neutralization of the slightexcess o'i nitric acid thereinby addition of aqueous or anhydrous ammonia, sentto storage, or where aqueous ammonia was usedfor forming the ammonium nitrate, direct to evaporators wherein the water contained in the solution is driven off'and theammonium nitrate crystallized. A

In other words, in accordance withY this invention, a method and apparatus is produced whereby nitric acid manufacture with neutralization for the formation of an inorganic'nitrate is combined. Acidied inorganic nitrate solution is circulated through a tower, through which nitrogen Yoxide gases and oxygen are: passed. The water heretofore necessary for showering the towerV to form nitric Yacid from said gases is supplied by the Water of the inorganic Vnitrate solution and the nitric acid formed in the solution is neutralized to an inorganic nitrate.

VHaving now indicatedV in a generatway v4the nature of the methodand apparatus in accordance with this invention, I will proceed tova detailed description thereof with reference to the accompanying drawings in which:

Figure 1 is-a diagrammatic showing of a 'form VofV apparatus for-carrying out the method of this invention.

Figure 2 is a diagrammatic showing of amodined form of apparatus. i' Y With reference to theY drawings in which there is diagrammatically illustrated a form of Vapparatus Yembodying this invention adapted for in connection with a description of which procedure involving the method will become apparent, a supply of ammonia, preferably anhydrous ammonia,` is contained in aY storage tank l. Ammonia in the Vtank I is vaporized by means ofV heat supplied by, for example, a steam coil 2.

Ammonia vapor passes from the tank l through a conduit 3 'to an air lter L4, from whichyln 'admixture V.with air, the ammonia vapor passes thro-ugh a conduit-5 into a 'converter li.A The converter may be of the-type commonly used'in ammonia oxidation byrn'eans of arfcatalyst, as,r

for example, platinum. i A

In the converter ltheammonia is oxidized to nitrogen oxide. The oxidation ofthe ammonia in the converter is initially, started by theV ap- Y carrying out the method ofV thisV invention and.`

plication of heat and thereafter continued under the influence of heat of reaction.

The hot nitrogen oxide gases pass from the converter 6 through a conduit l. The conduit 'I passes in heat interchange relation with a boiler 8 supplied with water through a conduit 9. In the boiler 8 steam is formed and passes through a conduit IU to any desired point of use. A portion of the steam passes through a valved conduit II to the coil 2 in the ammonia storage tank I.

The conduit 'I, carrying the hot nitrogen oxide gases from the converter 6 beyond the boiler, passes into heat interchange relation with an air heater I2, supplied with air from any suitable source through a conduit I3. The air heated in the heater I2 passes through a conduit I4 tothe air filter 4, in which it is admixed with the ammonia vapor passing to the converter 6.

Beyond the air heater the conduit 'I passes in heat interchange relation with exit gases from an absorption tower I5 in a heater I6. The exit gases from the absorption tower pass to the heater I 6 through a conduit 28. The heated exit gases pass through a conduit I1 for such use as it may be desired to put them to, as for example, for use in driving an air compressor for the supply of air under pressure to the conduit I3. The hot nitrogen oxide gases carried by conduit 'I beyond the exit gas heater I6, pass through an evaporator I8 in heat interchange relation with aqueous ammonium nitrate solution passing to the evaporator through a conduit I9 leading from a receiver 20.

The nitrogen oxide gases carried by the conduit 1 beyond the evaporator I8, lpass through a cooler 2I and from thence to the absorption tower I5. The cooler 2| is provided with a Water jacket 35 having inlet and outlet pipes 36 for water.

A supply of an aqueous solution of ammonium nitrate is provided in tank 22. The solution in tank 22 is acid.

From the tank 22 aqueous acid ammonium nitrate solution is drawn by a pump 23 through a conduit 24 and is forced by the pump through a cooler 25 and a conduit 26 to the absorption tower I5.

It will be noted that the conduit 26 joins the conduit I and that the acid ammonium nitrate solution and the nitrogen oxide gases are passed into the absorption tower together through a conduit 21 terminating at the top of the tower in a spray head BI). The absorption tower is of any usual and well known construction and may be provided with any suitable form of packing.

In the absorption tower the nitrogen oxide gases are absorbed by the water of the ammonium nitrate solution with the formation of nitric acid.

. As has been described, the exit gases from the lower end of the absorption tower pass through conduit 28 in heat interchange relation with the hot nitrogen oxide gases in heater I6, from whence they pass for use as a source of power.

'I'he ammonium nitrate solution with nitric acid absorbed in its passage through the absorption tower, passes from the bottom of the absorption tower through a bleacher 29, in Which nitrogen oxides are removed from the solution by means of air entering the bleacher from any suitable source of supply through a conduit 30 and passing from the bleacher with nitrogen oxides removed from the solution through a conduit 3| to thecbnduit 'I carrying the nitrogen oxide gases to the absorption tower I5.

From the bleacher 29 the ammonium nitrate solution carrying nitric acid passes into Vthe tank 22. Aqueous or anhydrous ammonia is intro-r duced into the tank 22 through a conduit 32. The ammonia introduced into the tank 22 reacts with the nitric acid contained by the solution entering the tank 22 from the bleacher 29 with the formation of ammonium nitrate.

From the conduit 2G, through which acid ammonium nitrate solution from the tank 22 passes to the absorption tower I5, a proportion of the ammonium nitrate solution is drawn into the receiver through a valved conduit 33.

The amount of ammonium nitrate solution drawn periodically or continuously into the receiver 20 depends upon the formation of ammonium nitrate in the tank 22 by reaction of ammonia, introduced into the tank 22, with nitric acid in the ammonium nitrate solution passing from the bleacher 29 into the tank 22.

The acid ammonium nitrate solution drawn into receiver 20 is neutralized in the receiver 29 by the addition of aqueous or anhydrous ammonia into the receiver from any suitable source through a conduit 34.

From the receiver 20, as has been indicated above, ammonium nitrate solution is periodically or continuously drawn through the conduit I9, which is provided with a suitable valve, into the evaporator I 8, in which the water of the solution is completely or partially evaporated by heat from the hot nitrogen oxide gases passing through conduit I in heat interchange relation with the evaporator. Where the heat of the nitrogen oxide gases is suicient to evaporate the ammonium nitrate solution in the evaporator, crystalline ammonium nitrate will be recovered from the evaporator. Should the nitrogen oxide gases in conduit l supply insuicient heat to the evaporator to completely evaporate the ammonium nitrate solution, partial evaporation will be accomplished and finally complete evaporation eiected in a supplemental evaporator of any suitable structure and supplied With heat from any suitable source.

In carrying out the method in accordance with this invention as described above, it is preferable, though not essential, to operate under pressure. Any suitable pressure may be used, but generally speaking a pressure within about the range 4-l0 atmospheres will be found efficient.

As has been indicated for the formation of ammonium nitrate by the addition of ammonia, to the ammonium nitrate solution containing absorbed nitric acid, as in tank 22, and for nal neutralization, as in receiver 2i), either aqueous or anhydrous ammonia may be used. Where aqueous ammonia is used the ammonium nitrate is recovered by evaporation of the water from the solution. On the other hand, where anhydrous ammonia is used, it follows that there is no addition of water to the system, hence, where the system is placed in operation with an initial amount of aqueous solution, if the concentration of ammonium nitrate in the solution is allowed to build up to say about 80%, the ammonium nitrate may be crystallized out of the solution by cooling and without evaporation of water. In such case the mother liquor is returned to the absorption portion of the cycle.

Referring now more particularly to Figure 2, in which the similar parts of the apparatus shown in Figure 1 are indicated by similar symbols, a part of the ammonium nitrate solution in receiver 20 may be periodically or continuously withdrawn, through a valved conduit 31, to a cooler 38, in which a portion of the ammonium nitrate vi'rill-be-precipitated, andfrom` thence to a centrifugal separator 39, in which the precipitated ammonium nitrate will be separated from the solution. The precipitated ammonium nitrate ln the form of crystals will be removed from the centrifugal to a drier 4U and from thence to storage. The solution or liquor will pass from the centrifugal to a receiver 4| and from there will be released, through conduit 43 by means of a pump 42, to the absorption tower I or to the receiver 20.` l

Also, in the arrangement shown in Figui-e2, the interior of theV cooler 2| is connected through a valved conduit 50 with a receiver 5I into which acid condensate from. the cooler 2l may be drawn. Condensate drawn into receiver 5l is neutralized by means of ammonia introduced into the receiver through conduit 52 and the neutralized condensate is then passed downwardly through an evaporating tower 53 supplied with reheated exit gases from theV gas Vreheater I6. The concentrated liquor from evaporator 53 passes through conduit 54 under the influence of a pump 55 to the receiver 20. Y

it will be 'appreciated that the apparatus'and method embodying this invention as above described with reierence to the production` of ammonium nitrate are adaptable for the production of other inorganic nitrates, as, for example, sodium, nitrate, potassium nitrate,` calcium nitrate, and the like. Thus, for the production of inorganic nitrates other than ammonium nitrate, it is only necessary to `substitute for the aqueous solution of `arrnnonia supplied to tank 22, andVv which is used for the production of nitric acid by absorption of nitrogen oxide gases in the ab- Y sorption tower I5, an aqueous solution of, an alkali as, for example, a hydroxide or carbonate of sodium, potassium, calcium, etc. and to effect neutralization in receiver of theacid salt solution drawn from the conduit 26 with a hydroxide or carbonate of sodium, potassium, calcium, etc. It will now be observed that inr accordance with`v this invention a method and apparatus for the productionof an inorganic nitrate are provided, by virtue` of which an inorganic nitrate' is produced withgreat efficiency and economy as compared with 4prior processes, vwhich involved the independent production and concentration of nitric acid and of inorganic' nitrate therefrom. In the apparatus and method in accordance with this invention, great saving is effected by virtue of the eiiicient use of the original heat. heretofore largely wasd, of the `nitrogen oxide gases, not onlyfor the' production of power, but also in connection with theV evaporation of the inorganic nitratesolution produced. 1

` It will be understood that the expression nitrogen oxide gases, and the like, as used inthe foregoing description, refer to the gas mixture produced as the result of oxidation of ammonia with oxygen or air in the catalytic converter, and

' which comprises essentially nitric oxide, oxygen,

and other nitric oxides, such as nitrogen dioxide, the several nitric oxides being present in varying amounts throughout the system depending on the temperature and pressure conditions obtaining at various points therein.

What I claim and desire to protect by Letters Patent is:

l. The process of manufacturing an inorganic nitrate including catalytically oxidizing ammonia with air to form a mixture of nitric oxide and oxygen, cooling said mixture, effecting absorption of nitric oxides in a. recirculating solution and oxygen, cooling said mixture, effecting absorption of nitric oxides in a recirculating solution of the inorganic nitrate', andv adding an alkali corresponding to the inorganic nitrate to the solution between the absorption passes thereof to react with nitric acid formed therein, the recirculating solution being maintained acid. l

3. The process of manufacturing ammonium nitrate from ammonia including catalytically oxidizing ammonia with oxygen to form a mixture of nitric oxide and oxygen, cooling said mixture,

effecting absorption of nitric oxides in a recirculating ammonium nitrate solution, and adding ammonia to the solution between the absorption passes thereof to react with nitric acid formed Y therein, 'the recirculating solution being maintainedV acid.V Y

4. The process of manufacturing ammonium vnitrate from ammonia including catalytically oxidizing-ammonia with air to form a mixture of nitric oxide and oxygen, effecting absorption of nitric oxides in a recirculating ammonium nitrate solution, and adding ammonia to the solution between the absorption passes thereof to react with nitric acid formed therein, the recirculating solution being maintained acid. Y

5. The processof manufacturing ammoni nitrate from ammonia including catalytically oxi-v dizing ammonia with air to forma mixture of nitric oxide and'oxygen, eiecting absorption of nitric oxides ina recirculating ammoniumi nitrate solution, and adding anhydrous ammonia to the solution between the absorption passes thereof to react with nitric Vacid formed therein, the recirculating solution vbeing maintained acid.

6. The process of manufacturing ammonium. nitrate from ammonia including catalytically'oxidizing ammonia with air torform a mixture of nitric oxide and oxygen, effecting absorption of nitric oxides in .a recirculating ammonium nitrate solution, adding ammonia to the solution between the absorption passes thereof to react with nitric acid formed therein, the recirculating solution being maintained acid, and withdrawing amimonium nitratesolution from the recirculating solution.

'7. The process of manufacturing ammonium" nitrate-from ammonia including catalytically oxidizing ammonia with air to form a mixture of nitric oxide and oxygen, effecting absorption of nitric Voxides in a recirculating ammonium nitrate solution, addingammonia to the solution between Ythe absorpton passes thereof to react with nitric acid formed therein, the recirculating solution being maintained acid, and continuously withdrawing ammonium nitrate solution from the recirculating solution.

8. The tprocess of manufacturing ammonium nitrate from ammonia including catalytically oxidizing ammonia with air to form a mixture of nitric oxide and oxygen, effecting absorption of nitric oxides in a recirculating ammonium nitrate solution, and adding ammonia to the solution between the absorption passes thereof to react with the nitric acid formed therein, the recirculating solution being maintained acid.

9. The process of manufacturing an inorganic nitrate including recirculating a solution of the.

inorganic nitrate, absorbing nitric oxides in such solution. and adding alkali corresponding to the inorganic nitrate to the solution between the absorption passes thereof to react with the nitric the recirculation solution such solution, adding ammonia to the solution between the absorption passes thereof to react withtheI nitric acid formedtherein, the recirculation solution being maintained acid, and continuously withdrawing ammonium nitrate solution from the recirculating solution.

',12. The process of manufacturing ammonium nitrate. including recirculating a solution of ammoniumr nitrate, absorbing nitric oxides in such solution, and adding ammonia to the solutionV between the absorption passesv thereof to react with4 the nitric acid formed therein, the recirculating solution being maintained acid.

13,'The process of manufacturing ammonium nitrate including recirculating a solution of ammonium nitrate, absorbing nitric oxides in such solution, adding'ammonia to the recirculating solution between the absorption passes thereof to react with thenitric acid formed therein, therecirculating solution being maintained acid, withdrawingammonium nitrate solution from the recirculating solution, and neutralizing the withdrawn solution with ammonia. l

14. The process. ofmanufacturingan inorganic nitrate including absorbingnitric oxides in an inorganic nitrate solution maintained acid during the absorption stepjadding analkali corresponding to-theinorganic nitrate to the solution after the, absorption step toreact with the nitric acid formed therein, cooling. the `solution for lprecipitation of theinorganic nitrate, separating precipitated inorganic nitrate from the solution and absorbing nitric oxides -in the separated solutions.

15. The-process of` manufacturing an inorganic nitrate including absorbing nitric oxides in an inorganic nitrate solution maintained acid during the absorption step, removing unabsorbed nitric oxides from said solution, adding an alkali corresponding to the inorganic nitrate to the solution after the removal of unabsorbed nitric oxides to react with the nitric acid formed therein, and evaporating the solution for recovery of the inorganicv nitrate.

l 16,.; process-of manufacturing ammonium nitrate including absorbingnitric oxides in a solution Ofammonium nitrate maintainedA acid during the,v absorption step, removing unabsorbed nitric oxides from said solution, adding ammonia to the solution after removal of unabsorbed nitric oxides to react with Lthe nitric acid formed therein, and eyapora'ting thesolution for recovery of ammonviuin` nitrate.

17. The processof manufacturing ammonium nitrate including recirculating a solution of ammonium nitrate, absorbing nitric oxides in such solution, removing unabsorbed nitric oxides from 1theirecirculating solution, adding ammonia tosaid'solution after removal of unabsorbed nitric oxides toreact with the nitric acid formed therein, the recirculation solution being maintained acid,- withdrawing a portion of the recirculating solution,` neutralizing. the withdrawn solution with ammonia, and. evaporating the neutralized solution forrecovery of ammonium nitrate.

18.. TheA process of manufacturing ammonium nitratel including catalytically oxidizing ammonia with oxygen to form a mixture of nitric oxide and oxygen, recirculating an acid solution of ammonium nitratey absorbing nitric oxides in such solution, remcving unabsorbed nitric oxides from the recirculating solution, adding ammonia to said solutionefter removal of unabsorbed nitric oxides to react Withthe nitric acid formed therein, withdrawing a portion of the recirculating solution, neutralizing the Withdrawn solution With ammonia,` andevaporating the neutralized solution by passing it in heat exchange relation with the hot. nitric oxides produced by said catalytic oxidation of ammonia for recovery of the ammcnium nitrate therefrom.

19.. Theprocess of manufacturing ammonium nitrate from ammonia including catalytically oxidizing ammonia with air to form a mixture of nitric oxideandfcxygen, eiecting absorption of nitric oxides ina recirculating ammonium nitrate solution, adding ammoniaA to the solution between the absorption passes thereof to react with nitric acid formed. therein, withdrawing ammonium nitrate solution from the recirculating solution, and evaporating said solution by passing it in heat exchange relation with the hot nitric oxides produced by` said catalytic oxidation of ammonia for recovery/'ofI the ammonium nitrate therefrom.

' 2,0. The processv ofv manufacturing ammonium nitrate .includingabsorbing nitric oxides in an ammonium nitrate solution maintained acid during the vabsorption step, adding ammonia to the solutionafter the absorption step to react with the nitric. acid formedtherein, cooling the solution for precipitation of ammonium nitrate, separating precipitated ammonium nitrate from the solution, and absorbing-nitric.oxides in the separated sblutons.

. JAMES H. SHAPLEIGH.

CERTIFICATE OF' CORRECTION.I

Patent No- 2,102,156.. December lh 1957.

JAMES H, sHAPLEiGH,

It is hereby certified that error appears in the printed speeifiation of the' above numbered patent requiring correction as follows: Page 3, second column, line 6l, claim 7, for "absorpton" read absorption; page h., first column, lines l5 and Z2-25, and second. column,` line l?, claims lO, ll and.KV

17 for "recirculation" read reoiroulating; andthat the said LettersA Patent should bevread with these corrections therein that the same may conform to the record ofthe ease lin the Patent Office., l

Signed and sealed this 8th day of February, A.. D.. 1958.

Henry Van Arsdale (Seal) Acting Commissioner of Patents, 

